1. Field of the Invention
The present invention relates to an engine cover mounting structure of an engine and an engine cover which covers the engine.
2. Description of the Related Art
It has become common in recent years that an engine cover is provided at a position between an engine and a bonnet in an engine compartment of a vehicle. This engine cover has a function to enhance the design property within the engine compartment by visually shielding the engine as well as a function to block noise that leaks (or is transmitted) from the engine.
The engine cover is mounted on an engine member. There are known various methods of mounting an engine cover on an engine member. For example, there exists a method of fastening an engine cover and an engine member together with bolts. In addition, there exists a method in which mounting portions are provided on one of a rear side of an engine cover and an upper surface of an engine member and portions to be mounted are provided on the other, whereby the engine cover is mounted on the engine member by bringing the mounting portions and the portions to be mounted into engagement with each other (for example, refer to JP-A-2004-278779).
In a engine cover mounting structure disclosed in JP-A-2004-278779, a mounting portion is made up of a hollow frame portion and a hollow elastic member which is inserted into the frame portion. A projection having a shape corresponding to a hollow interior of the elastic member is used as a portion to be mounted. Then, the mounting portion and the portion to be mounted are attached to each other by inserting the projection into the hollow interior of the elastic member. Since the elastic member is inserted in the frame portion, the portion to be mounted is mounted in the frame portion via the elastic member.
The frame portion is opened at a distal end thereof, that is, an end portion of the frame portion which is to face the portion to be mounted is opened. The elastic member inserted in the frame portion is formed into a cylindrical shape which is opened at two end portions thereof; an end portion facing the portion to be mounted and an opposite end portion thereto. Due to this, the projection is inserted into the elastic member through the opening in the frame portion. A restraining portion is provided on the frame portion in such a manner as to project into the hollow interior. A portion to be retrained is provided on an outer circumferential side of the elastic member at a position corresponding to the restraining portion in such a manner as to be brought into engagement with the restraining portion. The elastic member is held in the frame portion by virtue of the engagement of the restraining portion with the portion to be restrained. A cylindrical interior defined in the elastic member is formed into a shape which is expanded and contracted in an axial direction. An external shape of the projection is formed into a shape which corresponds to the cylindrical interior of the elastic member. Due to this, when the projection is inserted and passed through the elastic member, an internal surface of the elastic member and an external surface of the projection are brought into engagement with each other, whereby the portion to be mounted is mounted in the mounting portion.
The projection is formed into a shape which is diametrically expanded at an axially distal end and diametrically contracted at a central portion thereof. The internal surface of the elastic member is formed into a shape in which a diametrically expanded portion and a diametrically contracted portion are provided in an axial direction thereof in order to conform to the shape of the projection. Due to this, when the distal end (the diametrically expanded portion) of the projection is passed along the diametrically contracted portion of the elastic member in an attempt to insert the projection into the elastic member, the projection needs to be inserted while diametrically expanding the elastic member, and this increases a load (a press fit load) required for the insertion. Then, when the distal end of the projection has passed through the diametrically contracted portion of the elastic member, the press fit load is reduced. As this occurs, the elastic member elastically deforms to be contracted after the temporary expansion, and since the elastic member comes into spring contact with the projection when so contracted, a vibration of shock produced when the elastic member comes into spring contact with the projection is transmitted to the hand of the operator. Consequently, the operator is able to sense and realize through a change in press fit load and the vibration whether or not the mounting work has been completed. A touch perception imparted or sensed by the operator as this occurs is referred to as a click stop feeling in insertion in this specification.
Here, in an engine cover mounting structure like the one disclosed in Patent JP-A-2004-278779, the external shape of the projection is formed into a shape which corresponds to the cylindrical interior of the elastic member. Then, in order to ensure the fixing of the projection to the elastic member, the external shape of the projection is made larger than the cylindrical interior of the elastic member. Due to this, since the projection is inserted while being brought into press contact with the elastic member, the load (the press fit load) produced when the projection is inserted into the elastic member is increased, deteriorating the mounting work efficiency. The press fit load can be reduced by reducing a dimensional difference between an inside diameter of the elastic member and an outside diameter of the projection. In this case, however, the aforesaid click stop feeling in insertion is deteriorated, and this makes it difficult for the operator to sense and realize whether or not the mounting work has been completed. Consequently, also in this case, there has been caused a problem that the mounting work efficiency is not improved as desired.